🚀 go-pugleaf

In article <4857@dove.nist.gov> rosentha@bldrdoc.gov (Peter Rosenthal 303-497-5844) writes:
>In article <1992Jul28.075319.9973@fs7.ece.cmu.edu> snyder@henry.ece.cmu.edu (John Snyder) writes:
>>In article <7926@dirac.physics.purdue.edu> parks@gibbs.physics.purdue.edu (Chris Parks) writes:
>>>
>>>What is a good material (good=price + availability) which is
>>>an electrical insulator and a good conductor of heat?
>>>
>>>It will be used at temperatures as low as 4.2 Kelvin and it needs
>>>to hold up to about 200 volts / mm, heat conductivity needs to
>>>be comparable to copper.  Does it exist?
>>>
>>>Note: Diamond may be ideal but not practical!
>
>
>>Sapphire has been mentioned to me as such a material.  You do not mention in
>>what form: shape, size this material must be or how much of it you need.  
>>I believe that you can get man-made sapphire substrates.  They are probably
>>not cheap, but surely cheaper than diamond.
>>
>
>Actually, Sapphire is quite cheap.  A polished two-inch wafer costs
>about 125 bucks.  It is used in UHV viewports up to at least 4 inch 
       ^^^^^^^^^

I guess I should also have said, "It depends on your definition of cheap."
I generally work with 1 inch diameter wafers, either Corning 0211, 7059,
Silicon wafers, or polished fused silica.  The latter is most expensive,
and costs, (as of about 2 years ago, about $16.00 each).  So compared
to them, sapphire is not cheap.


>diameters.  Berylium oxide is another option.  Not transparent, but
>a great heat conductor.  Deadly toxic though.
>
>Peter Rosenthal
>
>
>-- 
>Peter Rosenthal       Email rosenthal@cmg.eeel.nist.gov
>